the frequency doubler is composed of a full wave rectifier followed by LM13700 OTA as VCAs. There’s a balance thing going on with the VCAs and the inputed CV. When one is +V the other becomes -V hence the panner effect.
I haven’t put values on the CV path for VCA because…i need to read more about those monsters. I’m not really keen on OTAs but they are quite easy to use and could do the job in spite of their low headroom and offset.
Here’s a video for understanding OTA and their gain configuration :
the author also had quite an amazing course series on electronic synth (imagine you going to college to learn how to build synth…) but the all series is unfortunately gone.
anyway, once again lot of switching jacks. It might turns out to be a real nightmare once built but I prefer pushing the modularity behond stupidty than realising afterward that I needed more.The VC panner can be used alone or with the double frequency circuit, use only the output of the latter and so on…
However, I’m not really convinced by the offset control over the input of the full wave rectifier. It gives that kind of waveform: